(a) Field of the Invention
The present invention relates to an apparatus and a method for controlling an engine clutch of a hybrid electric vehicle, more particularly, to an apparatus and a method that controls torque of an input shaft of the engine clutch to 0 by using an integrated hybrid starter and generator (HSG), and releases the engine clutch.
(b) Description of the Related Art
Generally, a hybrid electric vehicle is driven by an engine which generates torque from fuel combustion and an electric motor which generates torque from an electric battery.
The hybrid electric vehicle may be driven in a driving mode such as an electric vehicle (EV) mode, which is a true electric vehicle mode only using power of the motor, a hybrid electric vehicle (HEV) mode which uses rotational force of the engine as main power and rotational force of the motor as auxiliary power, and a regenerative braking (RB) mode for collecting braking and inertial energy while braking or coasting of the vehicle through electricity generation of the motor to charge the battery.
Generally, the hybrid electric vehicle is driven by power of the engine and the motor at a high speed, and performs regenerative braking to generate power by operating the motor during deceleration.
As such, the hybrid electric vehicle uses both mechanical energy of the engine and electrical energy of the high voltage battery, and uses an optimal operation area of the engine and the motor and collects the energy to the motor during braking, and as a result, fuel efficiency can be improved and energy can be efficiently used.
As described above, the hybrid electric vehicle performs regenerative braking while the hybrid electric vehicle is operating (particularly coasting), however, the motor cannot be operated as a generator when battery charging is limited due to a high state of charge (SOC) of the battery.
Therefore, the hybrid electric vehicle couples the engine clutch instead of performing regenerative braking and cuts off fuel for using engine friction torque when battery charging is limited while the hybrid electric vehicle is operating.
At this time, when the hybrid electric vehicle releases the engine clutch for accelerating, slip of the engine clutch occurs because of a hydraulic pressure decrease and a shock occurs because of the engine friction torque.
Conventionally, the motor performs torque compensation by reflecting transmission torque of the engine clutch in order to prevent the shock. However, the transmission torque of the engine clutch cannot be calculated accurately, so the torque compensation by the motor cannot be controlled accurately.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.